Low-Emission Propane-Driven Power Trowel

ABSTRACT

A power trowel for treating a concrete surface includes a support frame configured to be moved on the concrete surface. A propane supply vessel is supported by the support frame and is configured to contain propane. The propane supply vessel is positioned to reduce obstructions to the operator&#39;s view of the concrete surface. An internal combustion engine is supported by the support frame and is in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine. One or more rotatable shafts are driven by the internal combustion engine, and one or more trowel blades connect to the one or more rotatable shafts so as to rotate therewith.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application No. 61/329,183 filed Apr. 29, 2010, the disclosure of which is hereby incorporated by reference in its entirety.

STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

This disclosure generally relates to devices for finishing and/or preparing newly-created concrete surfaces, particularly power trowels.

Power trowels are typically used for finishing and/or preparing newly-created concrete surfaces. Some power trowels are used to spread epoxy on existing concrete floors. Such trowels are typically either walk-behind or ride-on devices, although remote-controlled power trowels are also available. Regardless of the specific manner in which an operator interacts with the device, most power trowels finish and/or prepare concrete using a similar type of mechanism. In particular, most power trowels include a prime mover (e.g., an internal combustion engine) that connects to a speed reducer (e.g., a gearbox) to rotate a vertical shaft supporting one or more finishing blades.

Despite being relatively efficient, gasoline-powered internal combustion engine trowels emit high levels of nitrous oxide, carbon dioxide, carbon monoxide, and solid particulates. These materials can be hazardous to the trowel operator and others in the immediate area, particularly if the trowel is used in an enclosed area such as the basement of a residential or commercial building. In addition, gasoline-powered internal combustion engine trowels can also subject newly-created concrete surfaces to “carbonation”, which is a chemical reaction that significantly reduces the strength of concrete. Carbonation occurs when carbon dioxide combines with water in newly-poured concrete to form carbonic acid. This acid reacts with alkaline components of the concrete and thereby prevents proper curing. Moreover, carbonation problems are magnified in situations in which plastic vapor barriers are placed below concrete to prevent moisture from wicking up through the concrete. In these situations, the plastic vapor barriers inhibit water shed by newly-poured concrete from draining to the substrate beneath the concrete. As such, the concrete retains a greater amount of water that may ultimately form carbonic acid.

Considering the above drawbacks of previous designs, there is a need for an improved power trowel.

SUMMARY

A power trowel is fueled by liquid propane, and thus emits a reduced amount of hazardous compounds compared to gasoline engine power trowels. As such, a power trowel according to the present disclosure facilitates an improved operating environment and is less likely to cause carbonation in newly-poured concrete.

One aspect of the present disclosure is a power trowel for treating a concrete surface. The power trowel includes a support frame, and a propane supply vessel is supported by the support frame and is configured to contain propane. An internal combustion engine is supported by the support frame and is in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine. One or more rotatable shafts are driven by the internal combustion engine, and one or more trowel blades connect to the one or more rotatable shafts so as to rotate therewith.

In another aspect, a power trowel for treating a concrete surface includes a support frame having a propane vessel support configured to support a vessel containing propane. A fuel regulator is supported by the support frame and is configured to receive propane from the vessel. The fuel regulator includes a vacuum-actuated valve that is actuatable to permit propane to exit the fuel regulator. The power trowel further includes an internal combustion engine supported by the support frame. The internal combustion engine is in fluid communication with the fuel regulator to receive propane exiting the fuel regulator to power the internal combustion engine. A vacuum conduit is in fluid communication with the internal combustion engine and the fuel regulator to transmit suction from the internal combustion engine to the fuel regulator. One or more rotatable shafts are driven by the internal combustion engine, and one or more trowel blades connect to the one or more rotatable shafts so as to rotate therewith. The vacuum-actuated valve is responsive to the suction from the internal combustion engine to control delivery of propane to the internal combustion engine.

In some embodiments, the propane vessel support is located in the forward area of the power trowel with a secondary option of directly behind the internal combustion engine. This inhibits the vessel from obstructing an operator's view of the concrete adjacent to the trowel.

In yet another aspect, a power trowel for treating a concrete surface includes a support frame having a front section and a rear section. A propane supply vessel is supported by the support frame and is configured to contain propane. The propane supply vessel is disposed in one of two vessel placement regions defined by the support frame. A first of the vessel placement regions is defined by the rear section of the support frame, and a second of the vessel placement regions is defined by the front section of the support frame and has an angular width of at most 90 degrees about the rotation axis. An internal combustion engine is supported by the support frame and is in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine. One or more rotatable shafts are driven by the internal combustion engine to rotate about a rotation axis, and one or more trowel blades connect to the one or more rotatable shafts so as to rotate therewith. The power trowel further includes an operator handle supported by the rear section of the support frame.

The foregoing and other aspects of the disclosure will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate exemplary constructions of the power trowel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a low-emission propane-driven power trowel according to the present disclosure;

FIG. 2 is a partial top view of the power trowel of FIG. 1;

FIG. 3 is a partial side view of the power trowel of FIG. 1;

FIG. 4 is a partial bottom perspective view of the power trowel of FIG. 1;

FIG. 5 is a schematic view of fuel delivery/power train components of the power trowel of FIG. 1;

FIG. 6 is a partial section view of a carburetor of the power trowel of FIG. 1;

FIG. 7 is a schematic view of alternative fuel delivery/power train components;

FIG. 8 is a section view of an alternative carburetor component; and

FIG. 9 is a top view of the power trowel of FIG. 1 illustrating regions in which a propane supply vessel may be placed relative to a support frame.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIGS. 1-4, a low-emission, walk-behind power trowel 10 includes a support frame 12 that mounts a liquid propane supply vessel 14. The liquid propane supply vessel 14 supplies liquid propane to an internal combustion engine 16 that in turn powers a plurality of rotatable trowel blades 18 to treat (i.e., finish and/or apply an epoxy to) newly-created concrete surfaces. By using propane as fuel, the internal combustion engine 16 emits significantly lower amounts of hazardous compounds compared to gasoline internal combustion engines. As such, the power trowel 10 provides a better operating environment and is less likely to cause carbonation in newly-poured concrete. These advantages and further details of the power trowel 10 are described below.

Still referring to FIGS. 1-4 and turning now to the support frame 12, the support frame 12 includes a plurality of frame rings 20 that define a blade guard around the trowel blades 18. The frame rings 20 also connect to a plurality of support brackets 22, and the frame rings 20 and the support brackets 22 connect to a set of mounting platforms. In particular, the frame rings 20 and the support brackets 22 support an engine mounting platform 24 (FIG. 3), a propane vessel mounting platform 26, and a battery mounting platform 28, that respectively support the engine 16, the liquid propane supply vessel 14, and a battery 30 operatively connected to the engine 16. In addition to the propane vessel mounting platform 26, the support frame 12 also includes a releasable over-center strap 32, such as those available from Alternative Fuel Systems Inc. of Arlington Heights, Ill., to secure the liquid propane supply vessel 14 to the support frame 12.

The support frame 12 also mounts a transmission housing 82 (FIG. 5) that in turn mounts an operator handle 34. The operator handle 34 includes an elongated rod 36 that extends diagonally away from the support frame 12. As shown most clearly in FIG. 3, the elongated rod 36 may connect to the support frame 12 via a pivotable support bracket 38 and removable pin 40 connection that permits the angle of the rod 36 to be varied and fixed at a comfortable height for the operator.

The elongated rod 36 also defines a vertical plane 42 (FIG. 2) that intersects with the rod 36, the support frame 12, and a rotatable shaft that supports the trowel blades 18. The vertical plane 42 can also intersect with the propane vessel mounting platform 26, the releasable over-center strap 32, and the liquid propane supply vessel 14. This is beneficial for several reasons. Specifically, the liquid propane supply vessel 14 does not significantly obscure the operator's view of the concrete near the support frame 12 when the vessel 14 is positioned along the vertical plane 42. In addition, when the liquid propane supply vessel 14 is positioned along the vertical plane 42 and spaced a calculated distance from the engine 16, the power trowel's overall center of gravity is positioned along a rotation axis 43 (FIG. 2) of the trowel blades 18. This calculated distance takes into consideration the empty weight of vessel, half-filled vessel weight, and fully-filled vessel weight. All these conditions produce a different center of gravity so the vessel 14 is positioned based on an average center of gravity. Such a configuration facilitates ease of maneuvering the power trowel 10 during operation. Nevertheless, the liquid propane supply vessel 14 may alternatively be located in other positions relative to the support frame 12 as described in further detail below.

Returning now to the operator handle 34, the end of the rod 36 opposite the support frame 12 supports an operator grip 44 having an outer oval shape. The operator grip 44 supports various controls for the power trowel 10, such as a dead man's switch 46.

Turning to FIGS. 1-5, fuel delivery/power train components of the power trowel 10 (e.g., the liquid propane supply vessel and the engine) and their interactions with liquid propane will now be described in further detail. First, the liquid propane supply vessel 14 is a propane tank designed for supplying fuel to an internal combustion engine, such as a 20# propane tank available from Manchester Tank of Franklin, Tenn. (e.g., P/N 9285) and pressurized to 250 psi. Other types of propane tanks may alternatively be used. In any case, the liquid propane supply vessel 14 includes an outlet including a manual shut-off valve 50. The outlet connects to a liquid propane delivery conduit 52 that in turn connects to a fuel regulator 54 on the opposite end. As such, the fuel regulator 54 receives liquid propane from the liquid propane supply vessel 14.

The fuel regulator 54 can be a model T60 regulator available from Beam Products of Cerritos, Calif., although other similar designs may alternatively be used. In any case, the fuel regulator 54 reduces the pressure of and vaporizes the propane received from the supply vessel 14. The regulator 54 then delivers the vaporized propane to the engine 16 based on a vacuum condition in the engine 16. In particular, the regulator 54 connects to a vacuum conduit 56 that transmits suction from the engine 16 to the regulator 54. This suction opens a vacuum-actuated valve 58 (FIG. 5) within the regulator 54 to permit the vaporized propane to enter a vaporized propane delivery conduit 60 connecting the regulator 54 and the engine 16. In addition, the valve 58 opens an amount that is proportional to the amount of suction, and the regulator 54 thereby delivers an amount of vaporized propane to the engine 16 that is proportional to the amount of suction.

Referring now to FIGS. 5 and 6 and turning to the engine 16, the engine 16 can be a four-stroke, single-cylinder engine that is similar to a gasoline internal combustion engine except for certain key features. One such feature is a fitting or “spud” 62 connected to a carburetor 64 of the engine 16. The fitting 62 connects to the vaporized propane delivery conduit 60 and receives vaporized propane therefrom. The fitting 62 can extend to and deliver the vaporized propane to the center of a venturi-shaped passageway 66 of the carburetor 64 that receives air to be mixed with the propane before combustion. The fitting 62 is also disposed at the throat 68 of the venturi-shaped passageway 66 (i.e., the area with the greatest amount of suction within the carburetor 64) which is disposed between the relatively large diverging 70 and converging 72 sections of the passageway 66.

Downstream of the diverging section 70 of the carburetor 64, through which the vaporized propane/air mixture passes, the carburetor 64 includes a vacuum fitting or spud 74 that connects to the vacuum conduit 56. As such, the vacuum fitting 74 and the vacuum conduit 56 place the regulator 54 in fluid communication with the carburetor 64 to sense a vacuum condition in the carburetor 64.

In addition to the above features, the carburetor 64 further includes one or more adjustment screws (not shown) that may be turned to vary the fuel-to-air ratio delivered to the cylinder or cylinders of the engine 16.

Besides the carburetor 64, the valve seat or seats of the engine 16 differ from those of a gasoline internal combustion engine. In particular, the valve seat 76 (FIG. 5) of each exhaust port can be hardened so that the valve seat 76 can tolerate the relatively high and otherwise damaging burning temperature of propane. The valve seat 76 may be hardened using processes such as induction hardening to provide a hardness of at least 50 Rockwell C Scale.

The engine 16 combusts the vaporized propane/air mixture received from the carburetor 64 to rotate an output shaft 78 (FIG. 5). The output shaft 78 connects to a clutch 80, such as a centripetally-activated clutch, and the clutch 80 in turn connects to a speed reducer 82, such as a gearbox. The speed reducer 82 drives a shaft 84 that rotates about the rotation axis 43, and the shaft 84 supports the trowel blades 18. As such, the trowel blades 18 rotate as the liquid propane supply vessel 14 provides propane to power the engine 16.

The structure of the trowel 10 may be modified in other manners that are not explicitly described above. For example and referring now to FIG. 7, the fuel regulator 54 may be an electronic fuel regulator. Here, the vacuum conduit 56 connects to an electrical switch 86 of the fuel regulator to provide fluid communication between the engine 16 and the electrical switch 86. Suction is thereby transmitted from the engine 16 to actuate the electrical switch 86. When actuated, the electrical switch 86 transmits a signal from the engine's battery 30 to a solenoid 90 within the fuel regulator. This signal actuates the solenoid 90 which in turn opens the vacuum-actuated valve 58 to permit vaporized propane to move toward the engine 16.

As another example, and referring now to FIG. 8, the carburetor 64 may include a fuel jet 92 connected to the vaporized propane delivery conduit 60 to deliver the vaporized propane to the venturi-shaped passageway 66. In these embodiments, the fuel jet 92 may be disposed at the diverging section 70 of the venturi-shape passageway 66.

As yet another example and referring now to FIG. 9, the liquid propane supply vessel 14 (and the mounting platform 26 and over-center strap 32) may be disposed in positions on the support frame 12 other than that shown in FIG. 2. However, at least a portion of the liquid propane supply vessel 14 can be disposed in one of two vessel placement regions 96, 98 such that the vessel 14 does not significantly obscure the operator's view of the concrete adjacent the trowel 10. One such region 96 is located on a rear section of the support frame 12 proximate the operator handle 34. This region 96 extends from the rear of the engine 16 slightly past the outermost frame ring 20 and has a width (perpendicular to the vertical plane 42) of 12 inches. The other region 98 is located on a front section of the support frame 12 proximate the engine 16. This region 98 extends from the front of the engine 16 slightly past the outermost frame ring 20 and has an angular width of 45 degrees from the vertical plane 42 on each side (for a total angular width of 90 degrees). That is, the propane supply vessel 14 and the center of the support frame 12 (i.e., the rotation axis 43) define an imaginary line that forms an angle of less than 45 degrees with the vertical plane 42. Moreover, the engine 16 may be offset from the position shown in FIG. 9, provided that the rotatable shaft 84 remains in the same position, to balance the weight of the propane supply vessel 14 and thereby position the power trowel's overall center of gravity along the rotation axis 43.

Furthermore, in some embodiments the clutch 80 may be a manually-engageable clutch, the regulator 54 could sense a vacuum condition in the crankcase of the engine 16, and/or the trowel 10 could even be a ride-on or a remote-controlled power trowel. Similarly, the trowel 10 could include multiple rotatable shafts 84 that each support a plurality of rotatable trowel blades 18.

From the above description, it should be apparent that the present disclosure provides a power trowel that, by using liquid propane as fuel, emits a reduced amount of hazardous compounds and thereby improves operating and curing conditions at the newly-poured concrete.

Exemplary embodiments have been described in considerable detail. Many modifications and variations in construction will be apparent to a person of ordinary skill in the art. Therefore, the disclosure should not be limited to the above description, but should be defined by the claims that follow. 

1. A power trowel for treating a concrete surface, the power trowel comprising: a support frame; a propane supply vessel supported by the support frame and being configured to contain propane; an internal combustion engine supported by the support frame and in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine; one or more rotatable shafts driven by the internal combustion engine; and one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith.
 2. The power trowel of claim 1, further comprising a fuel regulator in fluid communication with the propane supply vessel and the internal combustion engine to receive propane from the propane supply vessel and deliver propane to the internal combustion engine.
 3. The power trowel of claim 2, further comprising a vacuum conduit in fluid communication with the internal combustion engine and the fuel regulator to transmit suction from the internal combustion engine to the fuel regulator, and wherein the fuel regulator includes a vacuum-actuated valve being actuatable in response to the suction to permit propane to exit the fuel regulator and move toward the internal combustion engine.
 4. The power trowel of claim 3, wherein the internal combustion engine further comprises a carburetor in fluid communication with the fuel regulator to receive propane from the fuel regulator, and wherein the vacuum conduit connects to the carburetor to transmit the suction from the carburetor to the fuel regulator.
 5. The power trowel of claim 1, wherein the internal combustion engine includes one or more hardened valve seats.
 6. The power trowel of claim 1, further comprising an operator handle supported by the support frame and configured to be manipulated by an operator to move the power trowel on the concrete surface, and the operator handle defines a vertical plane intersecting the operator handle and at least one of the one or more rotatable shafts.
 7. The power trowel of claim 6, wherein the at least one rotatable shaft defines a rotation axis for the one or more trowel blades, the propane supply vessel is disposed in a region intersected by the vertical plane and having an angular width of at most 90 degrees about the rotation axis.
 8. The power trowel of claim 6, wherein the propane supply vessel is disposed such that it is intersected by the vertical plane.
 9. The power trowel of claim 8, wherein the internal combustion engine is disposed between the propane supply vessel and the operator handle.
 10. The power trowel of claim 1, wherein one of the one or more rotatable shafts defines a rotation axis for the one or more trowel blades, and the center of gravity of the power trowel is disposed along the rotation axis.
 11. A power trowel for treating a concrete surface, the power trowel comprising: a support frame including a propane vessel support configured to support a vessel containing propane; a fuel regulator supported by the support frame and configured to receive propane from the vessel, the fuel regulator including a vacuum-actuated valve being actuatable to permit propane to exit the fuel regulator; an internal combustion engine supported by the support frame and in fluid communication with the fuel regulator to receive propane exiting the fuel regulator to power the internal combustion engine; a vacuum conduit in fluid communication with the internal combustion engine and the fuel regulator to transmit suction from the internal combustion engine to the fuel regulator; one or more rotatable shafts driven by the internal combustion engine; one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith; and wherein the vacuum-actuated valve is responsive to the suction from the internal combustion engine to control delivery of propane to the internal combustion engine.
 12. The power trowel of claim 11, wherein the fuel regulator further includes a vacuum switch operatively connected to the vacuum conduit and actuatable in response to the suction to actuate the vacuum-actuated valve.
 13. The power trowel of claim 12, further comprising a battery supported by the support frame and operatively connected to the vacuum switch and the internal combustion engine.
 14. The power trowel of claim 12, wherein the internal combustion engine further comprises a carburetor in fluid communication with the fuel regulator to receive propane from the fuel regulator, and wherein the vacuum conduit connects the carburetor and the vacuum switch such that the carburetor transmits suction to the vacuum switch.
 15. The power trowel of claim 11, wherein the propane vessel support is a mounting platform configured to support the vessel thereabove, and further comprising a releasable strap configured to extend about the vessel to thereby secure the vessel to the support frame.
 16. A power trowel for treating a concrete surface, the power trowel comprising: a support frame having a front section and a rear section; a propane supply vessel configured to contain propane and being supported by the support frame such that the propane supply vessel is disposed in one of two vessel placement regions defined by the support frame, a first of the vessel placement regions being defined by the rear section of the support frame, and a second of the vessel placement regions being defined by the front section of the support frame and having an angular width of at most 90 degrees about the rotation axis; an internal combustion engine supported by the support frame and in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine; one or more rotatable shafts driven by the internal combustion engine to rotate about a rotation axis; one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith; and an operator handle supported by the rear section of the support frame.
 17. The power trowel of claim 16, wherein the propane supply vessel and the internal combustion engine are positioned relative to the support frame such that the center of gravity of the power trowel is disposed along the rotation axis.
 18. The power trowel of claim 16, wherein the operator handle defines a vertical plane that intersects the vessel placement regions.
 19. The power trowel of claim 18, wherein the first vessel placement region has a width perpendicular to the vertical plane of at most 12 inches.
 20. The power trowel of claim 16, where the first vessel placement region extends rearwardly from a rear of the internal combustion engine and the second vessel placement region extends forwardly from a front of the internal combustion engine. 